Manufacture of naphthalene



July 6, 1965 H. R. EMMERsoN 3,193,594

MANUFACTURE OF NAPHTHALENE Filed sept. 29, 1961 2 sheets-sheet 1 @M4auf@ ,47m/@wy July 6, 1965 H. R. EMMERSON MANUFACTURE OF NAPHTHALENE 2Sheets-Sheet 2 Filed Sept. 29, 1961 United States Patent 3,l93,594MANUFACTURE F NAPHTHALENE Hibbard R. Emmerson, Santa Ana, Calif.,assigner to Union Oil Company of California, Los Angeles, Calif., acorporation of California Filed Sept. 29, 1961, Ser. No. 141,826 20Claims. (Cl. 26d-672) This invention relates to an improved process forthe manufacture of naphthalene, and in particular concerns an improvedprocess for producing naphthalene by the dealkylation ofalkylnaphthalenes.

The expanding use of naphthalene for the production of dicarboxylicacids useful in manufacturing synthetic resins and fibers has createdconsiderable interest in the ,manufacture of naphthalene from petroleumhydrocarbons. It is well known that certain hydrocarbon fractionsobtained in various petroleum refining operations, eg., cracking andreforming, contain considerable quantities of alkylnaphthalenes Whichcan be thermally or catalytically dealkylated to form free naphthalene.As such processes are conventionally'carried out, a feedstock consistingof a reformate Aor cycle oil fraction boiling above about 430 F. andcomprising alkylnaphthalenes, alkylbenzenes, alkyltetralins,alkylindanes, etc., is subjected to dealkylating conditions to obtain aneiiluent product which, after separation of normally gaseous materialssuch as hydrogen and low molecular weight hydrocarbons, is fractionallydistilled to obtain: (l) a light gasoline fraction, (2) anaphthaleue-containing fraction, and (3) a heavy fraction comprisingunreacted alkylnaphthalenes which, after the removal of heavy ends andpolymers, is recycled to the dealkylation zone. Thenaphthalene-containing fraction is 'then processed, e.g., bycrystallization or fractional distillation, to isolate the naphthalenein substantially pure form, and the non-naphthalenic components aretaken as process products useful as heavy gasoline blending stock.

'of naphthalene and alkylnaphthalenes which can be recovered andemployed in the same manner as the naphthalene and alkylnaphthalenesproduced in the dealkylation step. Thus, in a process of the typedescribed above, in

Vwhich the dealkylation feedstock is a heavy reformate fraction and thenaphthalene is recovered from the naphthalene-containing fraction bycrystallization, I have found that increased yields of naphthalene(based on the amount of feedstock charged to the reformer) can beobtained by recycling to the reformer the mother liquor obtained fromthe crystallization step. As will be apparent, the reformer to which thenon-naphthalenic components of the napht'nalene-containing fraction arepassed need not necessarily be the one employed in preparing thedealkylation feedstock; it may be a reforming facility provided for thesole purpose of treating such components or it may be one located at anearby or remote location and employed for a different purpose. ln itsbroadest aspects, then, the process of the invention consists insubjecting an alkylnaphthalene-containing feedstock to dealkylatingconditions to obtain a naphthalene-containing eluent, fractionating saideffluent to obtain a naphthalene concentrate, separating substantiallypure naphthalene from said concentrate, and subjecting the remainingcomponents of the concentrate to reforming conditions.

In the accompanying drawings, FlGURE l thereof takes the form of aschematic flow diagram illustrating the process of the invention in itssimplest embodiment.

'hydrogen and normally gaseous hydrocarbons.

FIGURE 2 likewise takes the form of a ilowsheet, and illustrates apreferred embodiment. ln the interests of simplification, suchconventional process equipment as pumps, heat exchangers, reboilers,condensers, reflux lines, phase separators, valves, instrumentation,have for the most part been omitted.

Referring now to FIGURE l, the major items of processing equipmentinclude dealkylation reactor ld, dealkylate phase separator 12,fractionation system 14, naphthalene purification column 16, reformingreactor 20, and reformate phase separator 22. The process feedstock,consisting of an alkylnaphthalene-containing cycle oil extract(B.R.=4304S5 F.) obtained by solvent extracting a cycle oil produced bythe catalytic cracking of a Middle East crude, is introduced into thesystem via line 24 and passes to dealkylation reactor feed manifold 26.Within the latter, the feed is mixed with recycled material owing inrecycle line 28 and comprising recycled hydrogen introduced from line 3)and recycled alkylnaphthalenes introduced from line 32. Make-up hydrogenin an amount sufficient to compensate for that consumed in the reactionis introduced into recycle hydrogen manifold 30 from line 3d. Typically,the hydrocarbon portion of the dealkylation feed will comprise about 65volume percent of the fresh process feed and about 35 volume percent ofrecycled alkylnaphthalenes, and about 6000 s.c.f. of hydrogen areprovided perbarrel of hydrocarbon.

From dealkylation reactor feed manifold 26, the feed mixture passes topreheater 36 wherein it is heated to a temperature of about 900 F., andthe heated mixture is then passed via line 38 to dealkylation reactor10. The latter takes the form of a lire-brick lined shell iilled withone-inch alundum balls, and is maintained at a temperature Aof about1325 F. and a pressure of about 650 p.s.i.g. The mixture is passedtherethrough at such a rate as to maintain a contact time therein ofabout l0 seconds.

The hot dealkylation reactor eiiluent passes from reactor 10 to efuentcooler 40 wherein it is cooled to about F., and the cooled and condensedeffluent is passed to dealkylate phase separator l2. The normallygaseous components of the dealkylation reactor efiluent are withdrawnfrom separator 12 and are passed via line 42 to gas fractionation means4-4 to effect a partial separation of The latter are passed to storagevia line 46 for use as fuel gas or the like, whereas the fractionenriched in hydrogen (usually to an extent of about 70 to 90 percent) ispassed to hydrogen recycle line 30 for return to the dealkylationreactor.

The liquid portion of the dealkylation reactor efuent is passed fromseparator l2 to fractionation system i4 via transfer line 48, and withinthe latter is joined by a reformate stream flowing in line 50.Fractionation system 14 (which will usually take the form of severalindividual distillation columns) is operated to produce an overheadfraction consisting `of 400 F. end-point gasoline which is 'withdrawnfrom the system via line 52, a naphthalene concentrate fraction vboilingover the range 400-435 F., an alkylnaphthalene fraction boiling over therange 435- 5l0 F., and a bottoms fraction. The latter is passed tostorage via line 54 for use as fuel oil or the like, and thealkylnaphthalene fraction is passed to recycle line 32 for return todealkylation reactor 10.

The naphthalene concentrate fraction produced in fractionation system f4is passed via line 56 to naplithalene purification column 16 which isoperated to produce, in line 17, a heart-cut fraction distilling at420425 F. and comprising 98.2 percent naphthalene. The overheadfraction, comprising non-naphthalenic materials boiling at 400-420 F.and a small amount of naphthalene, is passed via line i8 to refromerfeed manifold 64. The

3 bottoms fraction, comprising non-naphthalenic materials boiling at 425-435 F. and a small amount of naphthalene, is likewise passed fromcolumn 16 to reformer feed manifold 64. VWithin the latter, thenon-naphthalenic hydrocarbons are joined by a stream of recycledhydrogen flowing in line 66. Reformer make-up hydrogen is introducedinto the system from line 65 in an amount sufiicient to provide atotalof about 6000 s.cv.f. of hydrogen per barrel of hydrocarbon. Frommanifold 64, the reformer feed'rnixture passes to preheater 70 whereinit is heated to a temperature of about 800 F., and the heated feed isthence passed to reformer 20.V Y

Reformer '20 is a conventional fixed bed catalytic reactor provided withmeans for maintaining an average bed ytemperature of about 950 F. lt isoperated at a pressure of about 900 p.s.i.g., and a liquid hourly spacedvelocityofV about 1.25 volumes of hydrocarbon per volume of catalyst perhour. The catalyst consists of weight percent of molybdenum oxidesupported on activated alumina.

The effluent from refromer 20 passes to effluent cooler 72, and thence.into reformate separator y22 wherein'it Aseparates into a liquid phaseand gaseous phase. VThe latter is passed to hydrogen recycle line 66 forreturn to feed manifold 64, with the net make gas being lpassed tostorage via line 'i4 for use as fuel. The liquid portion of thereformate, comprisingreformate gasoline, naphthalene, alkylnaphthalenes,and a small `amount of heavier ends, is introduced into line 5) fortransfer to fractionation system 14 and the recovery of these componentsas individual streams. .l

Considering now the process of the invention in greater detail, it isadapted to the dealkylation of any petroleum hydrocarbon mix-turecomprising a substantial amount of alkylnaphthalenes. Catalytically orthermally cracked cycle oils and heavy reformate fractions are mostcommonly employed, with platinum-catalyzed reformate fractions beingparticularly preferred. Y

A particularly preferred process feedstock of this type consists of aplatinum-catalyzed reformate fraction boiling between Vabout 435 F. andabout 530 F. and comprising -90 percent alkylnaphthalenes. A secondpreferred feedstock consists of a thermally or catalytically lcrackedcycle oil extract fraction obtained, for example, by subjecting a TCC orFCC cycle oil of suitable boiling range to hydrorefining (i.e.,hydrodesulfurization and/ or hydrodenitrogenation) in the presence of acobalt molybdate 4 catalyst (Unining), and subjecting the hydroreflnedprod- Y uct to solvent extraction (eg, with sulfur dioxidegor a glycol)to obtain :an extract product rich in naphthalene f and naphthaleneprecursors. Alternatively, the cycle oil can first be solvent extractedand the'aromatics-rich extract then hydrorefined to obtain a suitablefeedstock. With particularly clean kcycle oils (i.e., lowrsulfur and/ orlow nitrogen) the hydrorefining step can be omitted. Also,

when the dealkylation reaction is effected thermally, the

pre-removal of sulfur and/ or nitrogen from theV feedstock need not becomplete and in some instances (depending on the `sulfur land nitrogenspecifications for the naphthalene product) ymay be omitted entirely.

Since the composition of the product which is subjected to *reforming isnot substantially dependent on Whether the dealkylation reaction iseffected catalytically or thermally, vthe advantages of the process areattained with both types of operation. When carried out catalytically,the reaction is usually effected in the presence of hydrogen, and thecatalyst usually comprises an oxide or sulfide ofV one or more of themetals of groups VIB and 'VIII of the periodic system supported on anadsorbent carrier. Suitable active components include the oxides and/ orsulfides of tungsten, molybdenum, chromium, iron, cobalt, nickel, andmixtures thereof. These active compotures thereof. Supports lwhichnormally have relatively high cracking activity are preferably deactedby'including minor amounts of alkalizing compounds, e.g., sodium oxide,in the catalyst composition.y The catalyst may be maintained inthe formof a fixed bed, a compact moving bed, Aor a fluidized bed.V Typicalcatalytic dealkylation conditions include a reaction temperature betweenabout `s.c.f. of hydrogen (usually in the form o-f la recycle gascontaining 70-95 volume percent of hydrogen) are provided per barrel ofhydrocarbon. The use of water vapor to moderate the reaction inaccordance with the teachings of Doumani, US. Patent No. 2,734,929, is avaluable expedient, with the water vapor being provided in an amountrepresenting between about 0.04 and aboutY 0.15 barrel of liquid waterper barrel of hydrocarbon. When employing a fixed bed catalyst, it isalso desirable to maintain the temperature gradient within the bed at avalue below about 100V F. by-introducing a hydrogen-containing quenchgas into VtheV reaction zone at a plurality of points along the lengththereof.

drogen, with between about 2000 and about 10,000 s.c.f.

of hydrogen being provided per barrel of hydrocarbon.

It is also kconventional to effect thermal dealkylation withlin a fixed,compact moving, or fluidized bedof a noncatalytic'Y inert material, suchas sand, pebbles, alundum chips, and the like.

In general, then, the dealkylation reaction may be car- 'ried out underany of the widevariety of cond-itions known to effect the dea-lkylationof alkyl-substituted hydrocarbons such as alkylnaphthalenes.

The effluent which is withdrawn from the reaction zone is initiallytreated toseparate gaseous from liquid constituents, e.g.', bycondensation. When hydrogen is employed in the reaction zone it ispreferably recovered as a sep- ;arate gaseous stream for recyclepurposes by initially condens-ing the reactor effluent at an elevatedpressure, after which the normally gaseous hydrocarbons (which for themost part Vhave remained dissolved in the liquid hydrocarbon components)are fiashed off by reducing the pressure to a substantially lower value,e.g., atmospheric pres- Y sure.

The remaining liquid components of the reactor eluent are thenfractionated.

As previously stated, the fractionation operation is carried out toeffect the isolation of the following fractions:

l (1) alight gasoline fraction (typically having an end-point 'of about400 lF.) which is takenas a process product, (2) a naphthaleneconcentrate fraction which is passed to a naphthalene purificationoperation, (3) a heavy fraction which contains unconvertedalkylnaphthalenes and nonnaphthalenic hydrocarbons and which is recycledto the dealkylation zone, and (4) a high-boiling fraction which`comprises polymeric materia-ls and the like Yand which is taken'as aprocess productl useful as fuel oil or the like.

`While it is preferred that the naphthalene concentrate fraction be ofrelatively narrow boiling range, e.g., from about 380 F. to about 450F., preferably between about 400 Fgand about 435 F., and thatnaphthalene itself be the only naphthalenic component, the process ,isnonetheless operable should'the fractionation operation be carried outso that the naphthalene concentrate contains con- Y siderable amounts ofalkylnaphthalenes and has an end boiling point as high as about 500 F.

TheV naphthalene purication operation, whereby th Vsalts in the knownmanner to remove color bodies.

naphthalene contained in the naphthalene concentrate fraction isrecovered in substantially pure form, can be carried out in a number ofways. When the naphthalene product need be of only nom-inal purity,e.g., 90-98 percent, such operation may frequenlty consist merely of afractional distillation step carried out in the conventional manner.However, in some instances, there are present certain non-naphthalenicmaterials which form constant boiling mixtures with naphthalene, and insuch cases a naphthalene product of even such nominal purity can beobtained only by crystallization, selective solvent extraction ofazeotropic distillation. Crystallization is also resorted to when it isrequired that the naphthalene product have a purity greater than about98 percent. In recovering naphthalene from the concentrate fraction bycrystallization, the operation is carried out in the conventionalmanner, i.e., by cooling the feed stream to a relatively low temperatureto obtain a slurry of naphthalene crystals in mother liquor andthereafter separating the crystals by filtering or centrifuging.Preferably, the cooling is effected in a scraped surface chiller takingthe form of a jacketed .conduit through which the feed stream is passed.Scrapers ,adapted to be rotated aga-inst the walls of the conduit areprovided to prevent crystalline material from building up on the wallsof the conduit and interfering with the transfer of heat therethrough.Usually, the jacket is divided into two or more sections through whichdifferent refrigerants are circulated at successively lowertemperatures. The temperature to which the crystallizer feed stream iscooled and the rate at which such cooling is effected depend on thedesired purity of the product and the means and conditions employed forseparating the crystals from the mother liquor. In the practice of thepresent invention I have found it satisfactory to chill the feed to atemperature between about -20 F. and about 0 F., over a peniod of 30-60minutes when employing a centrifuge forl separating the crystals fromthe mother liquor. Usually it is desirable to wash the crystals with alight hydrocarbon wash liquid, eg., pentane, light gasoline, etc., andto remove traces of the wash liquid by steam stripping, distillation,etc.

If necessary, the naphthalene product obtained from the concentratefraction may be treated with clay or acidic In general, then, intreating the naphthaleneV concentrateY fraction to recover thenaphthalene therefrom, any of the techniques and equipment customarilyemployed in such type of operation may be employed, and any of theknown" treatments for the purification of petroleum or coal tarYVnaphthalene may be applied.

The reforming step, wherein the non-naphthalenic prodE ucts obtaniedfrom the naphthalene purification operation are Itreated to form furtheramounts of naphthalene and alkylnaphthalenes, is carried out as atypical hydroform-YA ing operation employing conventional conditions andcatalysts. Such conditions comprise: average reaction' Y temperatnresbetween about 825 F. andY about 975 F., i preferably between about 925F. and about 975 F.,

pressures between about 200 and about 800 p.s.i.g., space velocitiesbetween about 1.5 and about 5 volumes of hy- Ydrocarbon per volume ofcatalyst per hour, and hydrogento-oril ratios of between about 4000 andabout 12,000 s.c.f. per barrel. Any conventional reforming catalyst maybe used in either fixed bed, compact moving bed, or fluidized bed typeof operation. Typical active catalyst com-` catalyst comprises anactivated alumina base containing a minor proportion of fluorine andhaving between about 0.05 and about 1.0 weight percent of platinumdistended thereon. A second preferred type consists of cobalt molybdate(or a mixture of cobalt and molybdenum oxides) supported on activatedalumina, bauxite, or other clays,

and prepared as described in U.S. Patent No. 2,687,381.

Treatment of the reformate product to recover the various componentsthereof as separate entities is substantially the same as thatpreviously described in connection with the dealkylation reactoreffluent, i.e., it is condensed to effect separation of normally gaseousand liquid materials, and the latter are fractionated to obtain a lightgasoline fraction, a naphthalene concentrate fraction, and one or moreheavier fractions. As shown in FIGURE 1, fractionation of the liquidreformate may be carried out simultaneously with the fractionation ofthe dealkylate. The gaseous portion of the reformer effluent can beernployed as such for fuel purposes or, in accordance with moreconventional procedure, can be treated to separate at least part of thehydrocarbon components with the remainder being employed to supply partof the required hydrogen.

In the foregoing description of the process of the invention made withreference to FIGURE 1, reforming of the mother liquor was described asan independent operation, i.e., only the non-naphthalenic components ofthe naphthalene concentrate fraction were fed to the reformer. However,where the process is carried out closelyadjacent to reforming facilitiesnormally used for other purposes, such non-naphthalenic components, cansimply be passed to such facilities as part of the feed thereto. Thus,in FlGURE 1, reformer 2i? can well be a large facility serving primarilyto reform naphthenic hydrocarbons, and the non-naphthalenic componentsof the concentrate fraction will constitute merely a small part of thereforming charger. In such cases, the naphthalene and alkylnaphthalenesproduced from the non-naphthalenic components of the concentratefraction will be recovered along with, and used in the same manner as,the naphthalene and alkylnaphthalenes produced from the naphtha reformerfeed. FIGURE 2 shows a preferred embodiment of such type of operationwherein the naphthalene produced by reforming both the non-naphthaleniccomponents of the concentrate fraction and a naphtha is recovered alongwith the naphthalene produced by dealkylation of the alkylnaphthalenesproduced by said reforming. Y

Referring now to FIGURE 2, the major items of proc essing equipmentthere shown include a catalytic reforming'reactor 110, reformate phaseseparator 112, reformate fractionation system 114, dealkylatefractionation system 116, catalytic dealkylation reactor 118, highpressure and 'low pressure phase separators .120 and 122, respectively,"crystallizer 123, and centrifuge 124. The fresh feed, consisting of astraight-run naphtha boiling over the range 210 F .-375 F. `and havingan API gravity of about 45 is introduced into reformer feed manifold 126and is therein joined by a stream of mother liquor flowing in line 12Sand a stream of hydrogen flowing in line 130.

, About 8000 s.c.f. of hydrogen are provided per barrel of fresh feedand mother liquor. From line the reformer feed mixture passes to feedpreheater 132, wherein it is heated to a temperature of about 850 F. andthence into reformer 110.

Reformer 110 is operated at a pressure of about 465 p.s.i.g., and isprovided with inter-heaters, not shown, to maintain an average catalystbed temperature of about 900 F. The catalyst is a conventional platinumreforming catalyst comprising about 1 of platinum supported on aluminaand promoted with halogen, and the liquid hourly space velocity is about1.33 volumes of hydrocarbon per volume of catalyst per hour. Thereformer efllu- -ent passes from reformer 110 to separator 112 via line133, and within separator 112it separates into a hydrogenrich gaseousphase and a liquid hydrocarbon phase. The gas phase is withdrawn throughline 134 and, together with make-up hydrogen introduced from line 136,is passed to line for return to reformer 110. The liquid portion of thereformer effiuent is passed from separator 11,2 via i line 133 toreformate fractionation system 114. The latter is operated to produce inline a normally gaseous -128 for return to reformer 110.

j feed.

The bottoms fraction of the reformate is passed from VY73,193,59 Y

reformate fractionator 114 to dealkylate fractionation system 116 viatransfer line 142 wherein it is joined by the liquid portion of thedealkylator effluent flowing in line '144. As is apparent, dealkylatefractionation system 116 servesvthe dual purpose of fractionating-thedealkylated lproduct and'effecting further fractionation of the refor-'mate bottoms fraction. lt is operated to produce an over-V headfraction of 400 F. end-point dealkylate gasoline in line 146, anaphthalene concentrate fraction (BK-:400-

4-30 F.) in line 14S, an alkylnaphthaleneY fraction (B.R.=430540 F.) inline 150, and a bottoms fraction in line 152. The latter fraction ispassed to storageY for 'use as fuel oil or the like.Y

The naphthalene concentrate fraction owing in line '148 is passed toerystallizer 123, which takesV the form-'of a scraped `surface chiller,wherein it is chilled to a tem- The slurry of naphthalene crystals'inmother trate fraction produced in line 14S is introduced into line Thealkylnaphthaleue fraction flowing in line 150 con- Vstitutes thehydrocarbon feed vto the dealkylation step.

Said feed, together with'water Vand hydrogen flowing in and thepreheated mixture is passed to dealkylation re- 'actor 118. About 8100s.c.f. of hydrogen and about 0.085

lines 156 and 153, respectively, is passed to preheater 160 'wherein itis heated to an incipient reaction temperature,

S a pressure only slightly below that-of Areactor lllS. Within separator120, the eluent Vseparates into a gaseous phase, a liquidhydrocarb-onphase', and an aqueous phase. The Ylatter is withdrawn via line 156 andis either discarded .or recycled back to the reactor via line 156. VThegaseous phase, which comprises hydrogen and a relatively small Vamountof normally gaseous hydrocarbons, is withdrawn from'separator 120 and ispassed to line 162 `for use as the reactorquench gas and for recycle toreactor lliS via line 158; Make-up hydrogen is introduced 'into thesystem from line 163. The liquid hydrocarbon phase inrseparator .i120 iswithdrawn therefromand is passed through pressure relief Valve 170iritoY low pressureseparator 122 which is operated at a near atmosphericpressure. Within separator .122 the dissolved normally gaseoushydrocarbons flash `off to forma gaseous phase which is withdrawn and.passed via line 172 to storage for use as fuel gas or the like. rlfheliquid hydrocarbon phase whichforms in separator 122 is' passed to line144 for 'transfer tofractionation systemV 116 and recovery of thenaphthalene product.

The following table presents data which indicate quantitativelythe-results obtained by the process of the invention. These data wereobtained by reforming a'series "of blends prepared by mixingvaryingquantities of crystallizer mother liquor with a typical reformerfeed naphtha, and thereafter analyzing the 390 F.-[- fraction of Athereformate for naphthalene and C11 and higher alkylnaphthalenes. Themother liquor was one'obtained by catalytically dealkylating a 430-500F; reformate fraction under the conditions and with the catalystprevious- Yly described in connection With the dealkylation step of theprocess illustrated by FIGURE 2, .and thereafter crysftallizingnaphthalene from a 405 -430 F. fraction of 'the dealkylate. The reformerfeed with which the mother 'liquor was blended was a desulfurizedstraight-run naphtha boiling at 30W-380 F., and the reformer Wasoperated at anwaverage. bed temperature Vof about 905 F., 'a pressure ofabout 465 p.s.i.g., a hydrogen-to-oil ratio t' of about 10,000 s.c.f.per barrel of hydrocarbon, and at a liquid hourly space velocity of 1.32volumes of hydro- Y carbon per volume of catalyst per hour.

Run No Composition of Reformer Feed:

Naptha, vol. percent Mother Liquor, vol. percen t Analysis of ReformerFeed, Lb./100 gal.: .Y

Naphthalene C11 Alkylnaphrhalenpq C12 Alkylnanhfhalons TotalNanhfhale'nine Analysis of 390F.-|Fraction of '.Reformate, Lb./100 gal.

naphtha:

N aphthalene On Alkylnanhtbaleno C12 Alkyhlaphthalonn Total NaphthaleuimPotential Naphthalene,1 lbs/ gal, naphtha l 1 Assuming 100% recovery ofnaphthalene, and 100% conversion (by dealkylation) of allalkylnaphthalenes to naphthalene.

Reactor 118 contains a fixed bed ofa dealkylation catalyst consisting ofa silica-stabilized alumina base'having supported thereon :about 3.0Weight percent of cobalt oxide, about 9.0 weight percent of molybdenumoxide, and about 2.2 vweight percent of sodiumY oxide. The .reactionzone is maintained at a temperature of about 1l50 F'. and a pressure ofabout 1000 p.s.i.g., and a substantially uniform temperature profilewithin the catalyst bed is maintained by introducing a quench gasconsisting of Vpart of the hydrogen-containing recycle gas owing in line162 'into the reaction zone at a plurality of points along the lengththereof via lines 164. About 1430 s.c.f. of quench gas are employed perbarrel of hydrocarbon in the reactor The dealkylation reactor eluentpasses from reactor '118 to high pressure separator E120 which isoperatedV at VIn the appended claims, the term naphthalenic hydroncarbonis employed to designate a hydrocarbon compound containing the nucleus:

1 1 and hence includes vna-phthalene and the hydrocarbon 0- radicalsubstituted naphthalenes, but does not include hyployed, provided thestep or steps stated by any of the following claims, or the equivalentof such stated step or steps, be employed.

I, therefore, particularly point out and distinctly claim as myinvention:

1. In a process wherein an alkylnaphthalene is subjected to dealkylatingconditions to obtain a naphthalene-containing product, and said productis thereafter separated into a first fraction rich in naphthalene and asecond fraction lean in naphthalene, Vthe method of forming furtheramounts of naphthalenic hydrocarbons which comprises subjecting saidsecond fraction to reforming conditions.

2. In a process wherein an alkylnaphthalene-containing feedstock issubjected to dealkylating conditions in the presence of added freehydrogen to obtain a naphthalenecontaining product, said product isfractionated to obtain a naphthalene concentrate fraction boiling withinthe range of about 380 F. to about 500 F., and said fraction is treatedto separate naphthalene therefrom, the method of forming further amountsof naphthalenic hydrocarbons which comprises subjecting the remainder ofsaid fraction to reforming conditions in the presence of added freehydrogen.

3. In a process wherein a petroleum naphtha is passed through areforming zone and is therein contacted with a catalyst in the presenceof added free hydrogen and under reforming conditions of temperature andpressure to form a reformate product containing alkylnaphthalenes, saidreformate product is fractionated to obtain a fracti-on rich in saidalkylnaphthalenes, said alkylnaphthalenerich fraction is subjected todealkylating conditions in the presence of added free hydrogen to form adealkylate product containing naphthalene, said dealkylate product isfractionated to obtain a fraction rich in naphthalene but alsocontaining non-naphthalenic hydrocarbons, and said naphthalene-richfraction is treated to separate naphthalene therefrom, the method ofincreasing the proportion of naphtalenic hydrocarbons in said reformateproduct which comprises returning to said reforming zone at least aportion of the non-naphthalenic components of said naphthalene-richfraction.

4. A process as defined by cldaim 3 wherein said naphthalene-richfraction boils within the range of about 400 F. to about 450 F., and issubjected to crystallization to separate naphthalene therefrom, and saidnonnaphthalenic components are returned to said reforming zone in theform of the mother liquor from said crystallization.

5. A process as defined by claim 3 wherein said naphthalene-richfraction boils within the range of about 400 F. .to about 435 F. and issubjected to fractional distillation to separate naphthalene therefrom.

6. A process as defined by claim 3 wherein said reforming catalystcomprises platinum supported on alumina, and said alkylnaphthalene-richfraction is subjected to said dealkylating conditions in the presence ofa dealkylation catalyst comprising -a compound selected 'from the classconsisting of the oxides and sulfides of the metals of groups VIB andVIII of the periodic system distended on a catalyst support comprisingalumina.

7. The process for preparing naphthalene which comprises subjecting analkylnaphthialene-contaiuing feedstock to dealkylating conditions in thepresence of added free hydrogen to obtain a dealkylate productcontaining naphthalene derived from the alkylnaphthalenes contained insaid feedstock; fractionally distilling said dealkylate product toobtain a fraction containing said naphthalene in admixture withnon-naphthalenic components of said dealkylate product; treating saidfraction to separate said naphthalene from said non-naphthaleniccomponents; and subjecting at least a portion of the separatednon-naphthalenic components to reforming conditions in the presence offree hydrogen.

8. A process as defined by claim 7 wherein said frac- 10 tion boilswithin the range of about` 400 'P'. to about 450 F. and is subjected tocrystallization to separate said naphthalene from said non-naphthaleniccomponents, and said `separated non-maplithaienic components aresubjected to said reforming conditions in the form of the mother liquorfrom said crystallization.

9. A process as defined by claim 7 wherein said feedstock is a reformatefraction having an initial boiling point about 430 F., said 'fractionboils within the range of about 400 F. to about 450 F. and is subjectedto fractional distillation to separate said naphthalene from saidnon-naphthalenic components.

10. A process as defined by claim 7 wherein saidalkylnaphthalene-containing feedstock is subjected to said dealkylatingconditions in the absence of a dealkylation catalyst.

11. A process as defined by claim 7 wherein saidalkylnaphthalene-containing feedstock is subjected to said dealkylatingconditions in the presence of a dealkylation catalyst comprising acompound selected from the class consisting of the oxides and sulfidesof the metals of group VIB and VIII distended on a catalyst supportcomprising alumina.

12. A process as defined by claim 11 wherein said catalyst comprises amixture of the oxides of cobalt and molybdenum distended on a supportcomprising a major proportion of alumina and minor proportions of silicaand an alkali, and the dealkylation reaction is carried out in thepresence of water vapor.

13. A process as defined by claim 7 wherein said nonnaphthaleniccomponents are subjected to said reforming conditions in admixture witha petroleum naphtha.

14. A process as defined by claim 7 wherein said separatednon-naphthalenic components are subjected to said reforming conditionsin the presence of a reforming catalyst comprising platinum supported onalumina.

15. The process for preparing naphthalene which cornrises: (l)introducing a petroleum naphtha into a reforming zone and thereincontacting it with a reforming catalyst under reforming conditions andin the presence of added free hydrogen; (2) withdrawings from saidreforming zone a reformate product comprising naphthalene andalkylnaphthalenes; (3) fractionally distilling said reformate product toseparate a reformate fraction containing said naphthalene andalkylnaphthalenes and nonnaphthalenic hydrocarbons Iof the same boilingrange; (4) admixing said fraction with the hereinafter identifiedrecycle stream; (5) fractionally distilling the resulting mixture toobtain a first fraction rich in naphthalene and containingnon-naphthalenic hydrocarbons, and a second fraction rich inalkylnaphthalenes; (6) separating naphthalene from the non-naphthalenichydrocarbon components of said first fracti-on; (7) introducing at leasta portion ofthe separated non-naphthalenic hydrocarbon components intosaid reforming zone; (8) introducing said second fraction into adealkylation zone and therein subjecting it to dealkylating conditionsin the presence of added free hydrogen; (9) withdrawing from saiddealkylation zone a dealkylate product comprising naphthalene andalkylnaphthalenes; and (10) returning to step (4) as said recycle streama naphthaleneand alkylnapthalenecontaining portion of said dealkylateproduct.

16. A process as defined by claim 15 wherein, in step (6), saidnaphthalene is separated from said non-naphthalenic hydrocarboncomponents by subjecting said first fraction to crystallization; and, instep (7), said separated non-naphthalenic hydrocarbon components areintroduced into said reforming zone in the form of the mother liquorobtained in said crystallization.

17. A process as defined by claim 15 wherein, in step (8), said secondfraction is subjected to said dealkylating conditions in the presence ofadded water vapor and a dealkylation catalyst comprising a compoundselected from the class consisting of the oxides and sulfides of themetals of group VIB and VIII distended on a support comprising a majorproportion of alumina and minor proportions of silica and an alkali.

18. A process as'dencd byclaim 15 wherein, in step (1), Said reformingcatalyst comprises platinum supported on alumina. 1 Y Y 19. -A processas defined by (claim 15 wherein, in step (8), said second fraction issubjected to said dealkylating Vconditions in the absence of adealkylation catalyst.

Z0. A process as defined by claim 17 wherein, in step (1), saidreforming catalyst comprises platinum supported on alumina; in step (3)said reformate fraction boils `above about 385 F.; in step (5) said rstfraction boils Within the range of about 400 F. to about 435 F., andsaid second fraction boils Within therange of about 435 FI and about 540F.; and in step (8) said second fraction is subjected to saiddealkylating conditions in the presence of added Water vapor and aVdealkylation catalyst comprising the, oxides Iof cobaltl and molybdenumdistended on a support comprising a major proportion of alumina and'minor proportions 'of silica and an :alkali-metal alkali.

Y References Cited by the Examiner UNITED STATES PATENTS ALPHONSO D.SULLIVAN, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE 0F CGRRECTION Patent Nor,5,193,599r July 6, 1965 Hibbard Rn Emerson It is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column 9, line 43, for "cldam" read claim column 10, line 9, after"point" insert above column l0, line 4l, for "wthdrawings" readwithdrawing Signed and sealed this 21st day of December l965 (SEAL)Attest:

ERNEST W. SWIDER EDWARD I. BRENNER Attesting Officer Commissioner ofPatents

2. IN A PROCESS WHEREIN AN ALKYLNAPHTHALENE-CONTAINING FEEDSTOCK ISSUBJECTED TO DEALKYLATING CONDITIONS IN THE PRESENCE OF ADDED FREEHYDROGEN TO OBTAIN A NAPHTHALENECONTAINING PRODUCT, SAID PRODUCT ISFRACTIONATED TO OBTAIN A NAPHTHALENE CONCENTRATE FRACTION BOILING WITHINTHE RANGE OF ABOUT 380*F. TO ABOUT 500*F., AND SAID FRACTION IS TREATEDTO SEPARATE NAPHTHALENE THEREFROM, THE METHOD OF FORMING FURTHER AMOUNTSOF NAPHTHALENIC HYDROCARBONS WHICH COMPRISES SUBJECTING THE REMAINDER OFSAID FRACTION TO REFORMING CONDITIONS IN THE PRESENCE OF ADDED FREEHYDROGEN.